1) Fixed point Track
The chairs are built around a rectangular steel frame in the back of the chair where massage rollers, massage balls, or fixed-position heads are mounted. Fixed point Massage chairs use only stationary massage heads, so there’s no movement at all however the rollers rotate at fixed point.
The pressure pointsin your back either align with the heads, or they don’t. If they do, you’ll get a decent massage. If not, your experience will be sub-par.
You don’t find many fixed-frame chairs for sale these days, and when you do, they’re invariably at the extreme low end of the market.
2) S-Track
The S-Track is a steel frame that’s bent in an S-Shape so that it follows the natural curve of your body’s spine.
Mount rollers onto this frame, and they’ll move in three dimensions, adding the Z-axis at the points where your spine curves.
S-Track massage chairs are the most seen on the market today. They render a high-quality massage experience that starts at your neck and goes to the small of your back.
3) SL-Track
This is the most recent frame innovation. The frame gets its name from its overall shape, because the track continues past the small of your back, curving under the seat to allow the rollers to massage your glutes and the backs of your thighs.
These massage chairs often come with leg massage ports, extending the massage experience down to your calves, and sometimes even to your feet, giving you something closer to a full body massage experience.